[Bug]: node_voltage_stats.py - Passing polars df when expecting pandas

[owenfrausto]

Contact details

owenf@seas.upenn.edu

Tell us what you have found

Inside of NodeVoltageTimeSeries.compute(), the if statement is expecting to be passed a pandas dataframe but powerflow_results.get_voltage_dataframe() was reworked to polars. Solution included below

OS Platform

Windows 10 and above